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<a name="GDB_002fMI-Support-Commands"></a>
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<p>
Next: <a href="GDB_002fMI-Miscellaneous-Commands.html#GDB_002fMI-Miscellaneous-Commands" accesskey="n" rel="next">GDB/MI Miscellaneous Commands</a>, Previous: <a href="GDB_002fMI-Ada-Exceptions-Commands.html#GDB_002fMI-Ada-Exceptions-Commands" accesskey="p" rel="prev">GDB/MI Ada Exceptions Commands</a>, Up: <a href="GDB_002fMI.html#GDB_002fMI" accesskey="u" rel="up">GDB/MI</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="GDB_002fMI-Support-Commands-1"></a>
<h3 class="section">27.23 <small>GDB/MI</small> Support Commands</h3>

<p>Since new commands and features get regularly added to <small>GDB/MI</small>,
some commands are available to help front-ends query the debugger
about support for these capabilities.  Similarly, it is also possible
to query <small>GDB</small> about target support of certain features.
</p>
<a name="The-_002dinfo_002dgdb_002dmi_002dcommand-Command"></a>
<h4 class="subheading">The <code>-info-gdb-mi-command</code> Command</h4>
<a name="index-_002dinfo_002dgdb_002dmi_002dcommand"></a>
<a name="index-_002dinfo_002dgdb_002dmi_002dcommand-1"></a>

<a name="Synopsis-91"></a>
<h4 class="subsubheading">Synopsis</h4>

<div class="smallexample">
<pre class="smallexample"> -info-gdb-mi-command <var>cmd_name</var>
</pre></div>

<p>Query support for the <small>GDB/MI</small> command named <var>cmd_name</var>.
</p>
<p>Note that the dash (<code>-</code>) starting all <small>GDB/MI</small> commands
is technically not part of the command name (see <a href="GDB_002fMI-Input-Syntax.html#GDB_002fMI-Input-Syntax">GDB/MI Input Syntax</a>), and thus should be omitted in <var>cmd_name</var>.  However,
for ease of use, this command also accepts the form with the leading
dash.
</p>
<a name="GDB-Command-74"></a>
<h4 class="subsubheading"><small>GDB</small> Command</h4>

<p>There is no corresponding <small>GDB</small> command.
</p>
<a name="Result-8"></a>
<h4 class="subsubheading">Result</h4>

<p>The result is a tuple.  There is currently only one field:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>exists</samp>&rsquo;</dt>
<dd><p>This field is equal to <code>&quot;true&quot;</code> if the <small>GDB/MI</small> command exists,
<code>&quot;false&quot;</code> otherwise.
</p>
</dd>
</dl>

<a name="Example-74"></a>
<h4 class="subsubheading">Example</h4>

<p>Here is an example where the <small>GDB/MI</small> command does not exist:
</p>
<div class="smallexample">
<pre class="smallexample">-info-gdb-mi-command unsupported-command
^done,command={exists=&quot;false&quot;}
</pre></div>

<p>And here is an example where the <small>GDB/MI</small> command is known
to the debugger:
</p>
<div class="smallexample">
<pre class="smallexample">-info-gdb-mi-command symbol-list-lines
^done,command={exists=&quot;true&quot;}
</pre></div>

<a name="The-_002dlist_002dfeatures-Command"></a>
<h4 class="subheading">The <code>-list-features</code> Command</h4>
<a name="index-_002dlist_002dfeatures"></a>
<a name="index-supported-GDB_002fMI-features_002c-list"></a>

<p>Returns a list of particular features of the MI protocol that
this version of gdb implements.  A feature can be a command,
or a new field in an output of some command, or even an
important bugfix.  While a frontend can sometimes detect presence
of a feature at runtime, it is easier to perform detection at debugger
startup.
</p>
<p>The command returns a list of strings, with each string naming an
available feature.  Each returned string is just a name, it does not
have any internal structure.  The list of possible feature names
is given below.
</p>
<p>Example output:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) -list-features
^done,result=[&quot;feature1&quot;,&quot;feature2&quot;]
</pre></div>

<p>The current list of features is:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>frozen-varobjs</samp>&rsquo;
<a name="index-frozen_002dvarobjs"></a>
</dt>
<dd><p>Indicates support for the <code>-var-set-frozen</code> command, as well
as possible presense of the <code>frozen</code> field in the output
of <code>-varobj-create</code>.
</p></dd>
<dt>&lsquo;<samp>pending-breakpoints</samp>&rsquo;
<a name="index-pending_002dbreakpoints"></a>
</dt>
<dd><p>Indicates support for the <samp>-f</samp> option to the <code>-break-insert</code>
command.
</p></dd>
<dt>&lsquo;<samp>python</samp>&rsquo;
<a name="index-python"></a>
</dt>
<dd><p>Indicates Python scripting support, Python-based
pretty-printing commands, and possible presence of the
&lsquo;<samp>display_hint</samp>&rsquo; field in the output of <code>-var-list-children</code>
</p></dd>
<dt>&lsquo;<samp>thread-info</samp>&rsquo;
<a name="index-thread_002dinfo"></a>
</dt>
<dd><p>Indicates support for the <code>-thread-info</code> command.
</p></dd>
<dt>&lsquo;<samp>data-read-memory-bytes</samp>&rsquo;
<a name="index-data_002dread_002dmemory_002dbytes"></a>
</dt>
<dd><p>Indicates support for the <code>-data-read-memory-bytes</code> and the
<code>-data-write-memory-bytes</code> commands.
</p></dd>
<dt>&lsquo;<samp>breakpoint-notifications</samp>&rsquo;
<a name="index-breakpoint_002dnotifications"></a>
</dt>
<dd><p>Indicates that changes to breakpoints and breakpoints created via the
CLI will be announced via async records.
</p></dd>
<dt>&lsquo;<samp>ada-task-info</samp>&rsquo;
<a name="index-ada_002dtask_002dinfo"></a>
</dt>
<dd><p>Indicates support for the <code>-ada-task-info</code> command.
</p></dd>
<dt>&lsquo;<samp>language-option</samp>&rsquo;
<a name="index-language_002doption"></a>
</dt>
<dd><p>Indicates that all <small>GDB/MI</small> commands accept the <samp>--language</samp>
option (see <a href="Context-management.html#Context-management">Context management</a>).
</p></dd>
<dt>&lsquo;<samp>info-gdb-mi-command</samp>&rsquo;
<a name="index-info_002dgdb_002dmi_002dcommand"></a>
</dt>
<dd><p>Indicates support for the <code>-info-gdb-mi-command</code> command.
</p></dd>
<dt>&lsquo;<samp>undefined-command-error-code</samp>&rsquo;
<a name="index-undefined_002dcommand_002derror_002dcode"></a>
</dt>
<dd><p>Indicates support for the &quot;undefined-command&quot; error code in error result
records, produced when trying to execute an undefined <small>GDB/MI</small> command
(see <a href="GDB_002fMI-Result-Records.html#GDB_002fMI-Result-Records">GDB/MI Result Records</a>).
</p></dd>
<dt>&lsquo;<samp>exec-run-start-option</samp>&rsquo;
<a name="index-exec_002drun_002dstart_002doption"></a>
</dt>
<dd><p>Indicates that the <code>-exec-run</code> command supports the <samp>--start</samp>
option (see <a href="GDB_002fMI-Program-Execution.html#GDB_002fMI-Program-Execution">GDB/MI Program Execution</a>).
</p></dd>
</dl>

<a name="The-_002dlist_002dtarget_002dfeatures-Command"></a>
<h4 class="subheading">The <code>-list-target-features</code> Command</h4>
<a name="index-_002dlist_002dtarget_002dfeatures"></a>

<p>Returns a list of particular features that are supported by the
target.  Those features affect the permitted MI commands, but 
unlike the features reported by the <code>-list-features</code> command, the
features depend on which target GDB is using at the moment.  Whenever
a target can change, due to commands such as <code>-target-select</code>,
<code>-target-attach</code> or <code>-exec-run</code>, the list of target features
may change, and the frontend should obtain it again.
Example output:
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) -list-target-features
^done,result=[&quot;async&quot;]
</pre></div>

<p>The current list of features is:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>async</samp>&rsquo;</dt>
<dd><p>Indicates that the target is capable of asynchronous command
execution, which means that <small>GDB</small> will accept further commands
while the target is running.
</p>
</dd>
<dt>&lsquo;<samp>reverse</samp>&rsquo;</dt>
<dd><p>Indicates that the target is capable of reverse execution.
See <a href="Reverse-Execution.html#Reverse-Execution">Reverse Execution</a>, for more information.
</p>
</dd>
</dl>

<hr>
<div class="header">
<p>
Next: <a href="GDB_002fMI-Miscellaneous-Commands.html#GDB_002fMI-Miscellaneous-Commands" accesskey="n" rel="next">GDB/MI Miscellaneous Commands</a>, Previous: <a href="GDB_002fMI-Ada-Exceptions-Commands.html#GDB_002fMI-Ada-Exceptions-Commands" accesskey="p" rel="prev">GDB/MI Ada Exceptions Commands</a>, Up: <a href="GDB_002fMI.html#GDB_002fMI" accesskey="u" rel="up">GDB/MI</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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